1. Field of the Invention
The present invention relates to a flexible circuit structure and a method of manufacturing the same, and more particularly to a flexible circuit structure with stretchability and a method of manufacturing the same.
2. Related Art
Due to the developing trend of the electronics to become light, thin, short, and small and flexible, printed circuit boards (PCBs) that cannot be bent have gradually been replaced by highly-plastic flexible printed circuits (FPCs) boards, e.g., E-papers or flexible displays. In the applications of the FPC boards, the circuits must have specially-designed structures or made of special materials to withstand an external tensile force, so as to enhance the reliability in use.
In U.S. Pat. No. 6,743,982, a circuit is manufactured on a removable dielectric substrate. The circuit is formed by depositing two different metal materials. Then, the dielectric substrate under the circuit is removed. Thus, a coiled circuit structure is formed through deformation caused by different stress gradients of the metals, so as to achieve an overall stretchable effect.
In US Patent Publication No. US20040192082, a metal circuit is deposited on a pre-stretched flexible substrate. Then, the flexible substrate is released, so as to form a wave-shaped metal circuit structure. Upon being stretched by an external force in a specific direction, the wave-shaped metal circuit structure will be deformed accordingly, so as to prevent a break circuit from occurring to the metal circuit.
In both US Patent Publication No. US20040238819 and US Patent Publication No. US20040243204, a wave-shaped or saw tooth-shaped metal circuit is deposited on a flexible substrate, such that the stretchability of the metal circuit in the longitudinal or transverse direction is improved due to the deformation of the metal circuit. In the US Patent Publication No. US20040238819, the flexible substrate is firstly etched into a wave-shaped structure in a vertical direction, and then, the metal circuit is deposited on the wave-shaped flexible substrate, so as to improve the stretchability of the metal circuit.
According to the above methods, in most cases, the structural shape or material of the circuit is changed to enable the circuit to have better stretchability. However, the external stresses are mainly withstood by the circuit structure directly, so that the stretchability of the circuit structure is limited. Moreover, as an etching process is applied in most circuit process, if the width of the circuit is too small, the etching process becomes quite difficult to be achieved. Therefore, it is still an important trend for persons of this field to improve the stretchability of the circuit and to provide more convenient manufacturing methods.